Blade centric automatic test equipment system

ABSTRACT

An automated test equipment (ATE) system includes a plurality of test blades each coupled to a test blade connector and mounted on a circular track; a central reference clock (CRC) having an origin point at a center of the circle; and a clock/sync connector coupled to the CRC through a zero skew clock connection to one or more sync buses, wherein each instrument utilizes the CRC to coordinate its testing process with another instrument.

This application claims priority to Provisional Application 62/092,643filed Dec. 16, 2014, the content of which is incorporated by reference.

BACKGROUND

The present invention relates to ATE systems and methods.

FIG. 1 is a block diagram illustrating a system for explaining a testmethod of integrated circuit or chip equipment in a conventional art. Asdescribed in U.S. Pat. No. 6,883,128, conventional test equipmentincludes a PC equipment 201 having a chip equipment 210, a logicanalyzer 202 for trigging and obtaining a signal waveform of a terminal(pin) group of the chip equipment 210 as a certain fail information, apattern generation equipment 203 for inputting a signal waveform data(trace data) obtained from the logic analyzer 202 and converting to atest pattern of a desired test equipment and outputting the same, anautomatic test equipment (ATE) 204 for testing a chip equipment as atested device (DUT) 204-1 using a test pattern from the patterngeneration equipment 203 and judging whether an error occurs in the PCequipment, and a mass production ATE 205 for testing the products sameas the chip equipment 210 mounted in the PC equipment 201 as a testeddevice (DUT) 205-1. A test pattern is generated based on a trace data ofan operation state of a chip equipment mounted in a PC equipment forthereby testing a tested device. D data extracted from a logic analyzeris capable of only a small amount of a timing pattern which occurs inthe PC. Even when a desired amount of the timing pattern is extracted,since the environments between the PC and the ATE are very different, adesired reproduction is not obtained. In addition, the system isexpensive. The '128 patent solves this issue by implementing a memorypattern test using a pattern generation substrate in which a processoris designed in an EPLD for implementing a PC test and patternprogramming, so that a test evaluated under a PC environment formed of aCPU and chip sets. The PC test and automatic test are separated using ahigh speed switching device which is capable of implementing aconversion without a signal distortion between the signal lines extendedfrom the chip sets and the pattern generation substrate.

To certify the performance and functionality of modern semiconductordevices, reliable Automatic Test Equipment is required to maximize itsutilization. The circuitry of the DUT simulating and monitoring elementsall are powered by Direct Current (DC) supplies. Historically, these DCsupplies have been generated with a multitude of different individualbulk supplies with different voltage outputs to handle the requirementsof the different test elements. These many varied bulk supplies are amajor component to Automatic Test Equipment (ATE) failures.

SUMMARY

In one aspect, an automated test equipment (ATE) system includes aplurality of test blades each coupled to a test blade connector andmounted on a circular track; a central reference clock (CRC) having anorigin point at a center of the circle; and a clock/sync connectorcoupled to the CRC through a zero skew clock connection to one or moresync buses, wherein each instrument utilizes the CRC to coordinate itstesting process with another instrument.

In another aspect, an ATE system includes a central power supplypositioned at a center of a circular track; a plurality of test bladeseach coupled to a test blade connector and mounted on a circular track;and one or more power converters mounted on a test blade to generalpower on the test blade.

In a further aspect, an ATE system includes one or more blades as a testhead, a server coupled to a suite of Blades, and “Natural Feel” Softwareto tie the hardware together.

Advantages of the present system may include one or more of thefollowing. The system enhances test performance and decrease the testtime and error ratio and cost of the products. In contrast to the“rack-n-stack” instruments available for the engineering bench or afterthought add-ons to an existing test system, the Cobra's blades arecarefully architected to assure precise synchronization, short testtimes and production worthy stability. Rather than acceptgeneral-purpose solutions trying to solve a wide set of generic needs,Cobra blades focus on the key issues that minimize the real cost of eachtest challenge. This maximizes the utilization of the purchased capital,directly lowering the Cost Of Test for the user.

The system's centralized power distribution system assures that allinstruments have the precise set of voltages and currents desired, in alow-noise environment. This arrangement provides a simplified powerdistribution to provide a more reliable ATE system by limiting thediversity of bulk power supplies to one voltage. The custom tailoredpower requirements for now and the future based upon a single voltagereference provided to all major components of Automatic Test Equipment.Power distribution of a single voltage reference has been historicallyimpractical to implement given the circuit demands of Automatic TestEquipment, but this is made possible using the centralized powerdistribution of the present system.

Another advantage of the system is offered through the “CentralReference Clock” sub-system. A stable, precision oscillator provides the“heartbeat” for test functions and is broadcasted to all instruments.This reference clock is physically connected at the center of the CobraMotherboard—an origin point that facilitates a clock distribution thatapproaches “Zero Clock Skew”.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional tester system.

FIG. 2A shows an exemplary tester system.

FIG. 2B shows an exemplary tester with a four-blade cut away.

FIG. 2C shows the tester of FIG. 1 with a control computer.

FIG. 2D shows an exemplary cross-sectional side view of the system.

FIG. 3A shows an exemplary PCIe cable interface.

FIG. 3B shows an exemplary arrangement for minimizing noise for multipleblade instruments.

FIGS. 3C-3K show an exemplary hierarchical interface architecture formapping test addresses.

FIG. 4A shows a central power distribution system while FIG. 4B shows anexemplary electrical distribution scheme for the system of FIG. 4A andFIG. 4C shows another embodiment of the electrical distribution system.

FIG. 5A-5K show one embodiment of a central clock distribution system.

FIGS. 6A-6I show software programming constructs for the tester.

FIGS. 7A-7B show exemplary control processes for the tester.

DESCRIPTION

In the following description, details of various implementations are setforth to provide a more thorough explanation of embodiments of thepresent invention. However, it will be apparent to one skilled in theart that embodiments of the present invention may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form rather than in detail in orderto avoid obscuring embodiments of the present invention. In addition,features of the different embodiments described hereinafter may becombined with each other, unless specifically noted otherwise.

FIG. 2A shows an exemplary tester system called Cobra. The system has acylindrical housing 300 that receives a plurality of tester boards withinner edge 312 and outer edge 310. The system also has a plurality offans to cool the tester boards. One embodiment of Cobra is an advancedsystem for the automatic testing of semiconductor integrated circuits(IC). It is designed to be quick, quiet, and clean; providing customerswith a repeatable, high-throughput, low-cost production test solution.Cobra utilizes the peak of technology to deliver dependable andefficient performance in a small, rugged package. The Cobra offers a“blade” approach to the problem of IC testing. Digital pins, precisionDC sources, GHz amplifiers, time analyzers, among others, are allavailable as test instrument blades (TIB). Customers can select the setof TIBs to best satisfy their testing needs. This Application Specificapproach allows one tester platform to provide focused solutions forsuch varied test problems as NAND FLASH memories and multi-gigabitserial communications chips.

FIG. 2B shows an exemplary tester with a four-blade cut away. Fans 314are positioned on the outer edges of the system, in addition to exhaustvents 360 on top of the blades. The blades are concentrically arrangedas a radial array 364 and rest on a bottom mechanical support 380. Atthe center of the blades is a power and communication cable bundle 362and supported by a top mechanical support 366. A power distributionboard 368 is positioned on a central support tube 370, and the board 368is electrically connected to a system motherboard 372. A centralizedclocking system 374 is also connected to the motherboard 372, asdetailed below.

In one embodiment, the Cobra Test-head has 24 “slots” where tester'sblades can be inserted into to add functionality to the Test-head. TheTest-head supports a multitude of configurations with presently up to1920 digital channels in a 900 mm×550 mm cylindrical package. Thecylindrical nature of the system benefits the user by providing theshortest possible path between tester functions and the device undertest (DUT). Each blade is contained in it own metal chassis with localcooling, mechanical support systems, and shields the electronics fromEMF noise. Each Cobra test system will include a TIB chassis in allslots. Slots without active blades will hold “Dummy” blade chassis thatmaintain balance in the system. The system operates with any number ofactive blades from 1 to 24. The chassis protects the blade duringshipping and handling, also makes a very user-friendly replaceablemodule. Each of the blades contained in the test head is electricallyisolated from the other instruments or any other source. This “Floating”power system assures that each instrument is in the best possible“electrical noise environment” supporting high fidelity, high stabilityoperation of all tester functions. Combined with the shielding providedby the instrument chassis, Cobra is one of the quietest test systemsever constructed. To support the high-density packaging embodied in theTest-head, the cooling system utilizes a computer controlled set ofredundant, magnetically floating fans. Changes in room temperature orpower duty cycles are managed by altering fan speeds and turning onheaters near critical instrument circuits—assuring stable temperaturesand predictable instrument performance. The cooling controllers alsomonitor the 48 volt system supply to assure overall proper systemperformance. Should the temperature or the system supply be foundfaulty, the controller signals an “Alarm” and causes a system shut down.The controller also has a “Red or Green” indicator light which signalswhen the instruments are operating correctly or when there is a problemand the blade module needs replacement.

FIG. 2C shows the tester of FIG. 1 with a control computer 290 with adisplay 292. The computer 290 executes test software as described inmore details below, and instructions as well as results are passed backand forth with the tester 300 through a cable bundle 294. In oneembodiment, the cable bundle 294 is a PCI Express bus bundle that isshielded. PCI Express (Peripheral Component Interconnect Express),officially abbreviated as PCIe, is a high-speed serial computerexpansion bus standard designed to replace the older PCI, PCI-X, and AGPbus standards. PCIe has numerous improvements over the older busstandards, including higher maximum system bus throughput, lower I/O pincount and smaller physical footprint, better performance-scaling for busdevices, a more detailed error detection and reporting mechanism(Advanced Error Reporting (AER)[1]), and native hot-plug functionality.More recent revisions of the PCIe standard support hardware I/Ovirtualization. PCIe is based on point-to-point topology, with separateserial links connecting every device to the root complex (host). Due toits shared bus topology, access to the older PCI bus is arbitrated (inthe case of multiple masters), and limited to one master at a time, in asingle direction. Furthermore, the older PCI clocking scheme limits thebus clock to the slowest peripheral on the bus (regardless of thedevices involved in the bus transaction). In contrast, a PCIe bus linksupports full-duplex communication between any two endpoints, with noinherent limitation on concurrent access across multiple endpoints. Interms of bus protocol, PCIe communication is encapsulated in packets.The work of packetizing and de-packetizing data and status-messagetraffic is handled by the transaction layer of the PCIe port (describedlater). Radical differences in electrical signaling and bus protocolrequire the use of a different mechanical form factor and expansionconnectors (and thus, new motherboards and new adapter boards); PCIslots and PCIe slots are not interchangeable. At the software level,PCIe preserves backward compatibility with PCI; legacy PCI systemsoftware can detect and configure newer PCIe devices without explicitsupport for the PCIe standard, though PCIe's new features areinaccessible. The PCIe link between two devices can consist of anywherefrom 1 to 32 lanes. In a multi-lane link, the packet data is stripedacross lanes, and peak data-throughput scales with the overall linkwidth. The lane count is automatically negotiated during deviceinitialization, and can be restricted by either endpoint. For example, asingle-lane PCIe (×1) card can be inserted into a multi-lane slot (×4,×8, etc.), and the initialization cycle auto-negotiates the highestmutually supported lane count. The link can dynamically down-configurethe link to use fewer lanes, thus providing some measure of failuretolerance in the presence of bad or unreliable lanes. The PCIe standarddefines slots and connectors for multiple widths: ×1, ×4, ×8, ×16, ×32.As a point of reference, a PCI-X (133 MHz 64-bit) device and PCIe deviceusing four lanes (×4), Gen1 speed have roughly the same peak transferrate in a single-direction: 1064 MB/sec. The PCIe bus has the potentialto perform better than the PCI-X bus in cases where multiple devices aretransferring data communicating simultaneously, or if communication withthe PCIe peripheral is bidirectional. More details on the PCIe interfacewith the computer of FIG. 2C is detailed below.

FIG. 2D shows an exemplary side view of the system 300 where a centraltower 320 is formed with the inner edges 312 of a plurality ofconcentrically positioned tester blades 303. The system has a pluralityof test blades 303, each with plurality of connectors 320 that arepositioned near the outer edge 310 that allows the blades 303 tointercommunicate. In addition, a tester interface 322 communicates witheach blade through a top connector 324. The device under test (DUT) ispositioned on a DUT board 328 that communicates with the tester blades303 through a DUT cable snout 326. A DUT power system 330 and a centralclock distribution system 360 are positioned under the central tower 320and in electrical communication with the blades 303. The Cobra test headcan be thought of as a nest for 1 to 24 test instrument blades.

One implementation of the Cobra instruments contains various standardfeatures in addition to the circuits required to provide their specificfunctions, among others:

DC-to-DC conversion to create all the required voltages from the 48Vbulk supply

Local control processor with memory

Synchronization Controller for Inter-Instrument Communication

DC Isolated PCi Express for communications with a controller

Standard “Nest” connector for connection to:

Isolated Buss

48V bulk supply

Master Clock

16-bit wide sync bus

Relay isolated connection to Mother for validation

Selected connector to test fixture (load board).

The Testhead provides the TIBs: mechanical support, power distribution,cooling, high-speed communications, advanced clocking and coherentsynchronization. It is designed to provide a benevolent, supportiveenvironment for optimized performance. A stable, low-noise electronicenvironment is necessary to fully assure the quality of microelectroniccircuits during the test process, this is the core of The Cobra TestSystem. From its computer controlled cooling, to its ultra-low-noisepower distribution process and isolated communications bus, Cobra is therock-solid reference point demanded by integrated circuit engineeringand manufacturing. FIGS. 4A and 4B detail the power distribution thatprovides the stable low noise power supply to the tester blades 303.

FIG. 3A shows an exemplary PCIe cable interface. FIG. 3 shows therelationship between the Host Computer 290 and the Test System 300. Thesystem uses an adaptive semaphore signal to throttle the datatransmission between the Host computer and the Test System. Sinceseveral serial interface protocols are used within each Blade, it isbetter not to run the communication at the slowest rate to accommodatethe slowest device. This issue is avoided by using a “Self AddressingCircular Fifo” (SACF) 380 to receive data from the Host Computer. TheSACF 380 is located on the Host Interface Board. Since the Host can senddata faster than can be distributed through serial protocols, the systemneeds to throttle the data transfer. The SACF 380 stores several datatransactions before the system can slow down the transfers. After thesystem can process the data and empty the Fifo, the system can requestmore data transfers. The time for these interactive transfers isdependent on the Blade requirements. For fast transactions data can besent at 32 bits in about 200 nS in one implementation, but for longserial transactions the time becomes greater than 4 uS. Any requiredspeed can be accommodated using this technique. Using this method thesystem can always transfer data at the maximum speed allowed by thehardware on each Blade.

FIG. 3B shows an exemplary arrangement for minimizing noise for multipleblade instruments. The system is designed from the start with the bestpossible noise isolation presented to the Device Under Test (DUT). Thesystem contains 3 ground systems. The first is the Host Computer groundsystem, which should be avoided at the DUT. To accomplish this thesystem references the Host to Tester communication at the Host Computerground potential. On each Blade isolation is provided for all theDigital and Analog circuits using 2 novel methods. The first methodisolates the communication to the digital and digital input for theanalog circuits. This isolated digital data is then referenced to anisolated digital ground. This ground potential is referred to as thedigital isolated ground. In addition the system isolates the analogcircuits from the digital isolated ground using an analog isolatedground reference. These isolated grounds are only tied together at theDUT. This prevents noisy ground currents from affecting the criticalcircuits on the Blade or at the DUT. The actual means of isolating thesegrounds is accomplished using DC to DC converters with a transformer toprovide isolation between the primary and secondary. The power systemarchitecture is a distributed 48 volts to all Blades with the isolationDC to DC converters providing the isolated lower voltages as required.The DC to DC converter transformers are implemented using windingsprovided by the multilayer PCB with a transformer core that clamps tothe PCB. In one PCIe implementation, the following grounding scheme isused:

1. Most Instruments will have an Isolated Digital and an IsolatedAnalog. These will need to be tied together at the DUT.

2. The USB_GND will also need to be tied to the DUT ground if used.

3. The Slot#1 CAL ground signals on Ardent Block “A” pins A1 and A2should only be required for Calibration and are not required to be tiedto the DUT ground.

4. The User Sync associated Isolated Digital ground Ardent Block “B”pins B25 and B26 is only provided for a Scope sync. This signal is onlyavailable from selected Digital Instruments and should not be tied tothe DUT ground. The User Sync signal and the grounds should go to a setof test points.

5. The GND_POWER on the 25th Connector pins 4, 5, and 6 is only usedwhen controller device V48LB is required to generate special voltages onthe DUT card. It should not be tied to the DUT ground.

FIGS. 3C-3K show an exemplary hierarchical interface architecture formapping test addresses. Most Test Systems memory map the hardware withinthe range of the computer memory. In the past this has always become aproblem when the maximum allowed memory is exceeded. This is usuallycaused by the stored pattern memory becoming larger than the Computercan access. When this happens special operations are required such asMemory Paging or similar schemes. The preferred architecture only memorymaps a small amount of specific hardware. This scheme allows virtuallyunlimited test memory size. In a memory mapped architecture only 1memory address can be accessed at any single time. This means each usedpattern memory locations needs to be loaded with Test Pattern data. Theinstant architecture solves this problem by loading multiple locationsat once.

The instant system starts by assigning each Instrument a uniqueInstrument Enable, or Blade Enable or Blade Select Register. Using thistechnique multiple Blades can be selected. For example, the Cobra5 has 5Blade selects, The Cobra24 has 24 and the Cobra64 has 64. These areunique wires on a Top Hat PCB. The second level of hierarchicalselection is the Direct Board (Blade) Select registers. There are 16 ofthese registers assigned to each Blade. The Blade hardware and softwaredefine the purpose of these registers. As an example the General LogicBlade has the following assignment:

0 Instrument ID (normally Read Only)

1 Indirect Board Address 2 Indirect Board Data 3 Not Used 4 V/I_DPSSelect Register 5 V/I_DPS Indirect Address Register 6 V/I_DPS IndirectData Register 7 Not Used 8 Sequence Unit Enable Select 9 Sequence UnitIndirect Address 10 Sequence Unit Indirect Address 11 Not Used 12 PinSelect Register 13 Pin Indirect Address Register 14 Pin Indirect DataRegister 15 Not Used

The Indirect Address Registers eliminate the memory mapped hardwarelimitation by allowing 4 16 bit addresses for each Blade. This couldactually be expanded if required. The Select Registers are the basis forour increased Tester efficiency. Since these Select Registers can havemultiple selections, locations that require the same information can beloaded at the same time. This is very important in testing devices inparallel. The architecture of our tester is actually a tester for every8 pins. This allows each group of 8 tester pins to be independent. Thebest case scenario is testing an 8 digital pin device. That would meaneach GLB (General Logic Blade) would be able to test 10 devices. If thetest pattern was 1 Meg deep, the system could load the multiple devicesin a single pattern load. Other test systems would require loading 10×pattern memory for a 10× load time. If we have 5 Blades in our Cobra5system and they are testing 8 pin digital devices the system still onlyneeds a single pattern load. In this case other systems would require50× pattern load time. Thus, the advantage could become verysignificant.

The Sequence Unit Enable Select register selects up to 16 independentSequence Controllers. The GLB has 10 Sequence Control Units. TheSequence Control Unit controls 8 digital pins. This is what creates our8 pin tester architecture. These Sequence Controllers can be independentor concatenated with adjacent Sequence Controllers. This is required totest devices with larger than 8 digital pins. We have also provided forthe concatenation between the Blade Instruments. This would be requiredfor testing devices with more than 80 digital pins or test multipledevices that require partitions that span Blade Instruments. Since eachSequence Controller can be connected to the adjacent Sequence Controllerand span adjacent Blades Instruments, and since the Cobra24 and Cobra64are arranged in a circular configuration, we have a Circular Array of 8Pin Testers. Unfortunately the Cobra5 is not circular so the last Bladedoes not communicate easily with the first Blade. This could be fixed ona later revision if required.

The final level of digital selection is by pin. The Pin Select Registerallows multiple pins to be selected within each Sequence Controller. Onthe GLB there are 8 pins for each Sequence Controller but plans havebeen discussed where a Digital Blade would contain 16 digital pins foreach Sequence Controller. This would then become an array of 16 pintesters.

A similar structure is provided with the Device Power Supplies. Thereare 20 DPS (Device Power Supply) supplies arranged in 5 groups of 4.Again the V/I_DPS Select Register can have multiple selections allowingthe same data to program several supplies. Each of these suppliesrequires a gain and offset calibration. This information is stored inadditional hardware to allow the same programmed value to be written toeach supply as required. The modification of that value is done by thecalibration circuits to make the actual applied values correct at theDUT.

All of these functions can be expanded if required using the unusedDirect Board Registers. In one exemplary direct register mapping, thefollowing is used

0000 Instrument ID

0001 Indirect Board Address

0010 Indirect Board Data

0011

0100 F1(V/I_DPS Select Register)

0101 F1(V/I_DPS Indirect Address)

0110 F1(V/I_DPS Indirect Data)

0111

1000 F0(Sequence Unit Enable)

1001 F0(Sequence Unit Indirect Address)

1010 F0(Sequence Unit Indirect Data)

1011

1100 F2(Pin Select Register)

1101 F2(Pin Indirect Address)

1110 F2(Pin Indirect Data)

1111

Referring now to FIG. 4A, the central power distribution system 330 isdetailed. In this system, a master power generator is placed at thecenter of the blades. In one exemplary embodiment, the power generatorprovides 48V volts to all tester blades, and each tester blade in turnconverts the 48V up or down as needed.

FIG. 4B shows an exemplary electrical distribution scheme for the systemof FIG. 4A. The gray lines signify “dirty” and the blue is a “clean”environment. In this system, AC power is provided to a computer such asa Linux PC that drives an unfiltered high speed communication bus and aDC power supply that generates unfiltered non-lethal DC voltage, both ofwhich are provided to a blade mechanical enclosure. Circuits in eachblade extract an isolated high speed communication data for a particulartester blade n. Power circuits in each blade provide transformer basedpower isolation and locally generated power supplies that provide cleanlocal power for each tester blade n. Such isolated communication andpower buses are supplied to the DUT interface that in turn drives theDUT. In this manner, the Cobra instruments are completely isolated fromthe overall system and any other instrument. This DC isolationeliminates the possibility of parasitic current paths that limit thestability of non-isolated systems. DC stability maximizes thereproducibility of digital and analog circuits alike—the DUTs get thesame performance day-after-day, with no negative surprises.

FIG. 4C shows another embodiment of the electrical distribution system.In this embodiment, a simplified distribution of a single DC voltage isprovided to be distributed to all major components of the system. Thepower network is regulated and kelvin sensed to provide a stable,reliable, bulk power source. One or more bulk supplies are located in aremote chassis for ease of service and replacement. The AC controlmodule is configured for the country of use, containing all of thefunctions required to turn the system on and off and provide necessarysafety elements (e.g. emergency power down). The power is delivered tothe Device Under Test (DUT) electronics via a bundled cable of power andcommunication wires. The individual voltages required by a given DUTelectronic component are created directly on that DUT electronics'component. This assures that all instruments have the precise set ofvoltages and currents desired, in a low-noise environment. Thisarrangement provides a simplified power distribution to provide a morereliable ATE system by limiting the diversity of bulk power supplies toone voltage. The custom tailored power requirements for now and thefuture based upon a single voltage reference provided to all majorcomponents of Automatic Test Equipment. Power distribution of a singlevoltage reference has been historically impractical to implement giventhe circuit demands of Automatic Test Equipment, but this is madepossible using the centralized power distribution of the present system.

FIG. 5 shows one embodiment of a central clock distribution system. Theclock system includes a central reference clock origin point 410 withzero skew clock connection 412 to a clock/sync connector 414 that isconnected to one or more sync buses 416. Each instrument utilizes theCentral Reference Clock (CRC) to coordinate its testing process with allthe other instruments. The CRC starts each test sequence and provides asingle frequency reference. Each Cobra Blade is free to utilize the CRCas its master clock or augment it with “On-Blade” enhanced clocking.These enhanced clocks allow different blades to run at differentfrequencies. It can be said that each Cobra Blade can run in its own“Time Space”. Test sequences can be created where different DUT portsare tested with a unique timing reference. Advanced problems such asarbitration logic testing suddenly become simple and easy to solve.

Each blade is electrically isolated from all others, yet can communicatewith each other during testing by use of a sophisticated system ofsynchronization. A multi-level sync bus, allows the blades to preciselysignal each other to coordinate their testing sequences. Sync Events canbe used for combining error lines or to lock two Cobra Blades togetherin time.

In some cases a single blade could control the sync for all theinstruments. Or, repetitive groups of blades could be linked togetherfor high-throughput, parallel testing—whatever configuration bestsupports the testing approach being used.

In the case of very small pin count devices, each blade can act alone intesting the devices it is connect to, without waiting for the resultsfrom others. This can improve the system's production capacity by 5% ormore in some cases—a significant economic advantage for customers.

FIGS. 5B-5J show one exemplary Clocking System architecture that usesboth central and distributed clocks. The Master Clock Board providesthree very accurate and stable clocks. In one embodiment, a crystalcontrolled Reference Clock is generated from a 125 MHz crystaloscillator. The system divides this frequency by 2 to provide the 62.5MHz system reference clock. Dividing the clock by 2 removes any bi-modaldistortion from the final reference. This clock is buffered anddistributed to the Blades in a “Star Configuration” with matchedtransmission lines on the Master Clock board and the Backplane. Thisclock is used on the Blades for all the serial communication to thedigital and analog circuits. The Master Clock divides the 62.5 MHz by 2to provide a 31.25 MHz reference to the Host Interface Board. The 31.25MHz reference is provided on the ribbon cable connecting the Top HatCircuit Board to the Master Clock Board. The second clock is provided bya DDS circuit which generates the Master Clock variable frequency. Thisclock frequency is from 80 MHz to 120 MHz. It has a resolution of 2hertz. The 120 MHz to 80 MHz range allows the selection of any VectorRate frequency from 1.2 KHz to 50 MHz with 2 hertz resolution. The DDScircuit uses a bandpass filter to remove unwanted frequencies and a highspeed comparator to create a digital square wave. This Master Clock isalso distributed to the Blades in a “Star Configuration” with matchedtransmission lines. It is used by each Sequence Controller on the GLB tobe divided as the Vector Rate Clock or TZero clock. The third clock isalso 62.5 MHz but is sourced from the DDS circuit to provide known phasealignment with the internal DDS clocks. It is also distributed to theBlades in a “Star Configuration” with matched transmission lines. Thisclock is only required for starting an optional Master Clock Modulelocated on each Blade. This allows integer related or non-integerrelated clocks for specific testing requirements. There are also controlsignals to guarantee synchronous operation. These are I/O Update, ClockStart and Clock Stop.

The system incorporates extensive synchronization hardware and software.In addition to the clocking synchronization mentioned earlier there aremultiple Instrument synchronization signals. The Instrumentsynchronization is used to communicate between the Blades. This allowsdigital hardware to initiate and respond to analog hardware. The reverseis also true. The digital hardware can request the analog hardware tomake a measurement and the analog hardware can indicate to the digitalhardware when the measurement is complete. Many examples of the Bladeinteraction are possible. The Instrument synchronization is partitionedby performance capability. The highest performance is called “SegmentedMultisource”. These signals are used for the Error signals and Sync1.These signals have the lowest propagation delays and can be sourced frommultiple locations. The actual hardware design uses differential ECLwire or signaling. The partitioning capability is provided by thebackplane and the Blade. These signals can drive or receive from theprevious or next Blade Instrument. The backplane provides a previous ornext signal to the Blade. The Blade can connect these together toprovide a continuous signal along the backplane or break the connectionto create independent previous and next signals. The Sync1 signal is notas programmable as the other Sync signals but does have the highestperformance. The second highest performance synchronization signal isthe Segmented Single Source. There are 8 of these signals labeled Sync2through Sync9. They can be segmented in the same manner as the Sync1signal, but there can only be a single driving source. There can bemultiple receiving destinations. These signal are also differential butare not wire or. The signaling level is Bus Low Voltage DifferentialSignaling (BLVDS). The Blade determines where the source driveoriginates and where the destination terminates. This selection is madeby the Host. The Host programs multiplexors in the Digital Spartan3FPGA, and enables the drive and receive buffers on the Blade. The lastsynchronization signal type is the General Purpose Continuous Sync.There are 8 of these signals labeled Sync10 through Sync17. They cannotbe segmented and run the length of the backplane. They are BLVDS and canonly have a single driving source. There can be multiple receivedestinations. These are the lowest performance sync lines.

FIG. 5K shows an exemplary skew handling system. One set of timingconsideration is the interface between the 100EP142 Low Voltage PositiveEmitter Coupled Logic (LVPECL) and the input of the PCIe Driver/ReceiverIC. Since the output voltage levels of the PCIe driver are is subject tovariation due to temperature, FPGA process, and propagation delaymismatch the system provides a method to account for some of thevariations. The system uses a differential output Q7 to sum the high andlow level voltage through equal value resistors to determine the exactcenter of these 2 levels. The system uses this center voltage as thereference voltage input for the Mercury IC. This provides voltagetracking of the two devices eliminating timing skew.

The various systems incorporate vector rate timing generated with anFPGA. This timing is subject to variation due to temperature, FPGAprocess, and propagation delay mismatch. The system uses a retimingscheme that I believe in unique in the Test Industry. The FPGA needs tointerface to (LVPECL) through Low Voltage CMOS (LVCMOS) for the outputsfrom the FPGA device.

This provides a Voltage Out High (VOH) of 2.1 volts.

Voltage Out Low (VOL) will be 0.4 volts.

A 100 ohm series resistor with a second 100 ohm resistor to +2.5 voltsis inserted, and the junction feeds the LVPECL input of an 100EP142register.

The resulting levels for the 100EP142 inputs are Voltage In High(VIH)=2.3 volts

The resulting levels for the 100EP142 inputs are Voltage In Low(VIL)=1.45 volts

Input level specification on the 100EP142 is (VIH)=2.075 to 2.42 voltsand (VIL)=1.355 to 1.675 volts

To interface from the 100EP142 to the FGPA the system performs thefollowing:

Voltage Out High (VOH) for the 100EP142 is 2.155 to 2.405 volts.

Voltage Out Low (VOL) for the 100EP142 is 1.355 to 1.605 volts.

The system uses a 51 ohm series resistor with a second 100 ohm resistorto ground. The junction feeds the FPGA input with the input selected tobe SSTL2_I.

The resulting levels for the FPGA inputs are Voltage In High (VIH)=1.509volts

The resulting levels for the FPGA inputs are Voltage In Low (VIL)=0.98volts

Input level specification for the FPGA are VIH=VReference+0.15 volts andVIL=VReference−0.15 volts

The VReference is set to 1.25 volts.

The input voltage has a symmetrical swing around the VReference voltage.

The retiming PCIe driver registers are clocked at 2× the Master Clockfrequency to provide a 5 nS Re-Time clock. The system automaticallyadjusts all the FPGA outputs within this embodiment's 5 nS window.

An Isolated Serial Communication architecture is detailed next. To speedup the serial communication across the isolated boundary we have decidedto send the 32 bits of data in 4 groups of 8. By using this method itonly takes 8 serial clocks (62.5 MHz) instead of 32 clocks. This didhowever create a situation where the propagation delay between the 4channel ISO7240 ICs could cause a skew of data so the clocking would notbe reliable. The system handles this issue by sending 2 serial datastreams with an associated clock through each ISO7240 device. Since thedata and clock will now be delayed the same amount the clock skew issuewas resolved. During the readback of Blade data a similar situationarose. The system loops the clock signal back through the ISO7240devices so it would also track the data path. The readback can beoptimized on the GLB since it requires 35 clocks instead of the writecycle which only requires 8.

Next, system calibration is detailed. Calibration is a considerationthat must be designed into both the hardware and software. The Bladedesign incorporates special calibration hardware to allow the softwareto perform the calibration procedures. In all Cobra Systems the Bladelocated in Slot or Blade position #1 will have calibration hardwareenabled. This provides a single reference timing signal for the entiresystem. The system Master Clock (80-120 MHz) and system Reference Clock(62.5 MHz) can be selected to drive a differential LVPECL signal to DUTboard. This signal is only available from the Blade in Blade position#1. A User Sync clock can also be selected by the host to provide asynchronizing signal for test program debug. This signal is available oneach Blade Instrument if required.

Next, the software components for communicating with the test hardwareis detailed.

FIG. 6A shows one implementation of Cobra with four basic productgroups: the Testhead, the Sever, a Suite of Blades, and Test Software totie the hardware together. The system uses many software registers andthey belong to a C++ hierarchy. Each software register knows how to dotwo things; read and write.

The basic register can perform reads and writes to a specific hardwarelocation, as illustrated in FIGS. 6B-6E. Every register may be tagged asvolatile or nonvolatile. Volatile indicates that the value in theregister may change on its own, without tester intervention. Most Cobraregisters are nonvolatile.

The cache is simply a memory location used by the register to keep acopy of the data last written to the register. Each register has its owncache. Reading from the cache is much faster than reading from hardware.Also, redundant writes to hardware can be optimized out by realizingthat the data to be written already matches the data in cache. The useof caches thus provides greater I/O performance. These are the buildingblocks for all of various register types. A new object, a register list,is used which is a list of one or more registers. A register list canalso perform read and write operations. A register list read returns alist of data, one value for each register in the list. Register listwrites come in two forms. One form takes a single data value to bewritten to all registers. The other takes a list of data, one value foreach register.

Default register list read procedure

For each register in list

-   -   Perform register read        Default register list write procedure (one value)

For each register in list

-   -   Perform register write        Default register list write procedure (value list)

For each register & data in list

-   -   Perform register write

One embodiment constrains register lists to only contain registers ofthe same type.

An indirect register is read/written through two hardware locationsreferred to as the address register and the data register, as shown inFIG. 6F

The value in the address register points to an indirect registerlocation. Data written to the data register will be forwarded to theindirect register pointed to. Likewise, data read from the data registerwill be read from indirect register that is pointed to.

The use of indirect registers allows an unlimited amount of indirectregisters with just a few real address lines. Most of the system'sregisters are indirect. The software indirect register has pointers totwo other software registers. One is named the address register and theother is named the data register.

Indirect register write procedure

Tell the address register to write the value which is my indirectaddress.

Tell the data register to write the data I want to write.

Indirect register read procedure

Tell the address register to write the value which is my indirectaddress.

Tell the data register to read.

Like indirect registers, selectable registers have a data registerthrough which reads and writes are performed indirectly. A selectregister determines the location(s) that will be targeted from the dataregister.

FIG. 6G shows the select register containing the binary value 10011. Thebits are connected to enable lines on the selectable registers. There isone bit for each selectable register. If that bit is a zero, theselectable register does not respond. If it is a one, it does respond.

For read operations, software must ensure that only one bit is set inthe select register to avoid bus collisions. For write operations,however, any number of bits may be set. This allows the broadcast writecapability illustrated above.

In software, the selectable register type is almost identical to theindirect register type. It has pointers to two other software registers.One is named the select register and the other is named the dataregister.

Selectable register write procedure

Tell the select register to write the bit which selects my selectableregister.

Tell the data register to write the data I want to write.

Selectable register read procedure

Tell the select register to write the bit which selects my selectableregister.

Tell the data register to read.

Selectable registers are used heavily in the instant system. It startswith the host interface board which has a select register for everyinstrument card slot in the system. This select register must be setbefore doing any I/O to Cobra instruments. It also means that any writeoperation that an instrument supports may be broadcast simultaneously tomultiple instruments.

To illustrate this concept further, the register operations will bediscussed for a General Logic Blade (GLB). It provides 80 instrumentpins, divided into ten groups of eight. Each group of eight iscontrolled by a group controller. The board has an I/O controller whichreceives communication from the card bus. It has a group select registerwhich selects the group controllers to talk to. Each group controllerhas a pin select register to control which of the eight pins to talk to.Let's now look at a single register for a GLB pin, as shown in theexample of FIG. 6H. The group controllers maintain eight copies of manypin registers. Therefore the pin registers are indirect. There is onecontrolling the format for a pin. This is the register we will focus on.It is at an indirect address of 5 within the group controller. Butbefore the system can write that, it needs to select the correct board,group, and pin. Since there are 80 pins on the GLB, the softwaremaintains 80 format register objects per GLB. To set the first pin onthe first GLB to NRZ format, we must write the value 4 to the firstregister. The software locates the correct register object and does awrite operation with a value of 4. The format register is a selectableregister. The procedure for writing to a selectable register is to firstwrite a value to the select register and then write the data register.So the system must first write the value 1 to the pin select register.That register is also a selectable register. Before the system can writethat, it needs to write the value 1 to the group select register. Thatregister is also a selectable register. Before the system can writethat, it is instructed to write a 1 to the board select register.

Once the system finish the writes, it can pop back to the second step ofwriting the format register, which is to write 4 to the data register.The data register is an indirect register. The procedure for writing toan indirect register is to first write a value to the address registerand then write the data register. We need to write the value 5 to thepin address register and then write the value 4 to the pin dataregister. But wait, the pin address register is a selectable register.It will once again instruct us to first select group 1. Group one isalready selected and since that register is nonvolatile we can skip thatoperation. This logic continues until all of the necessary addressinghas been done and our value has been written.

The pin format register, illustrated in FIG. 6I, masquerades as a simpleselectable register which points to two other register objects. Inreality, it represents a tree structure which in turn directs the simpleprocedures for writing all of the necessary registers with the rightvalues and in the correct order. This tree is set up at programinitialization time. Not every register has an identical tree. There areother kinds of registers not mentioned here. But after initialization, Ican take any register in the system and just say read or write and allof the appropriate actions take place to make it happen.

The parallelism is achieved through the register list operations. Forreading, nothing changes since reading must be done one register at atime. But we just need to make some simple changes to the register listwrite routines to take advantage of all of the information already codedinto the register objects. First we introduce a new register listoperation called select. It takes only a register list, no data.

Default register list select procedure

No operation

Register list select procedure for selectable registers

Create an empty select register list

Create an empty select value data list

For each register in list

-   -   Is this register's select register in the select register list?        -   If no, append this register's select register to the list            -   and append this register's select value to the data list        -   If yes, OR this register's select value into the data for            the register.

Perform a register list write of the OR′ed select values to the selectregister list

Perform a register list select operation on the select register list

Now we need to supply the register list write routines for selectableregisters. The default ones stay the same.Register list write procedure for selectable registers (value list)

For each value in list

-   -   Create a register list of registers writing that value    -   Perform register list write of one value        Register list write procedure for selectable registers (one        value)

If the registers are nonvolatile

-   -   For each register in list        -   Check data against cache. If data matches, remove register            from the list

Perform a register list select operation on this register list

Write the data to the first register in the list (writes to allregisters)

Update all cache values

The ATEworks with a DUT and one or more blades in a test-head. The DUThas a testing program, and includes a plurality of functional modules.The testing blades or module is connected to the device under test, andtests the plurality of functional modules of the device under testsequentially or in parallel. The DUT executes the testing program andcommunicates with the testing blade. The testing blade tests theplurality of functional modules of the DUT and testing is performedautomatically without testers, and hence the personnel cost and thetesting time can be reduced.

The system can test memory devices such as DRAMs and flash memorydevices. The system can also test PC motherboards and other embeddedelectronic products. The system can be used to test analog electronicdevices as well as wireless electronic devices to determine whethertheir functions are operating properly. For example, a test probe may beattached to a wireless device to determine whether its radio-frequencytransceiver circuitry is able to properly generate radio-frequencyoutput signals. Tests may also be performed that involve transmittingand receiving actual radio-frequency signals. For example, the systemcan act as a “call box” is used to send and receive protocol-compliantradio-frequency test data to a wireless device under test. Call box testequipment can handle bidirectional signaling-type test transmissionssimilar to full-fledged cellular telephone calls. If the call boxdetermines that the device is not performing properly, the device may berepaired or discarded.

FIG. 7A-7B show exemplary control software for the tester. Turning nowto FIG. 7A, the process selects one or more test blades in 502. It thenselects processing units in 504 and resources in 506. The process thenbroadcasts data to all selected resources in 508.

Referring now to FIG. 7B, another control embodiment is shown. In thisembodiment, the process selects tester blade(s) in 522 and processingunits in 524. The process also selects resources in 526. The processthen checks that all blade resources are selected in 528 and if not, itloops back to select processing units and resources. and otherwise theprocess proceeds to check if all resources have been selected in 534. Ifnot, the process loops back to 522 and otherwise the process broadcastsdata to all selected resources in 538.

Further embodiments of the present invention provide a method fortesting a device under test. In a first step, an input signal isreceived from the device under test and information describing the inputsignal is written to a memory. In a second step, the informationdescribing the input signal is read from the memory and an output signalis provided for the device under test based on the informationdescribing the input signal read from the memory.

Further embodiments of the present invention provide an apparatus forconfiguring the ATE. The apparatus is adapted to configure the automatictest equipment to receive an input signal from a device under test andto write information describing the input signal to a memory. Theapparatus is further adapted to configure the automatic test equipmentto read the information describing the input signal from the memory 16and to provide an output signal for the device under test based on theinformation describing the input signal read from the memory.

Further embodiments of the present invention provide a method forconfiguring the automatic test equipment. In a first step, the automatictest equipment is configured to receive an input signal from a deviceunder test and to write information describing the input signal to amemory. In a second step, the automatic test equipment is configured toread the information describing the input signal from the memory and toprovide an output signal for the device under test based on theinformation describing the input signal read from the memory. Althoughsome aspects have been described in the context of an apparatus, it isclear that these aspects also represent a description of thecorresponding method, where a block or device corresponds to a methodstep or a feature of a method step. Analogously, aspects described inthe context of a method step also represent a description of acorresponding block or item or feature of a corresponding apparatus.Some or all of the method steps may be executed by (or using) a hardwareapparatus, like for example, a microprocessor, a programmable computeror an electronic circuit. In some embodiments, some one or more of themost important method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments of theinvention can be implemented in hardware or in software. Theimplementation can be performed using a digital storage medium, forexample a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM,an EEPROM or a FLASH memory, having electronically readable controlsignals stored thereon, which cooperate (or are capable of cooperating)with a programmable computer system such that the respective method isperformed. Therefore, the digital storage medium may be computerreadable.

Some embodiments according to the invention comprise a data carrierhaving electronically readable control signals, which are capable ofcooperating with a programmable computer system, such that one of themethods described herein is performed.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein. The data carrier, the digital storagemedium or the recorded medium are typically tangible and/ornon-transitionary.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods described herein. The data stream or thesequence of signals may for example be configured to be transferred viaa data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured to or adapted toperform one of the methods described herein.

A further embodiment comprises a computer having installed thereon thecomputer program for performing one of the methods described herein.

A further embodiment according to the invention comprises an apparatusor a system configured to transfer (for example, electronically oroptically) a computer program for performing one of the methodsdescribed herein to a receiver. The receiver may, for example, be acomputer, a mobile device, a memory device or the like. The apparatus orsystem may, for example, comprise a file server for transferring thecomputer program to the receiver.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are preferably performed by any hardware apparatus.

The above described embodiments are merely illustrative for theprinciples of the present invention. It is understood that modificationsand variations of the arrangements and the details described herein willbe apparent to others skilled in the art. It is the intent, therefore,to be limited only by the scope of the impending patent claims and notby the specific details presented by way of description and explanationof the embodiments herein.

What is claimed is:
 1. An automated test equipment (ATE) system,comprising: a plurality of test blades each coupled to a test bladeconnector and mounted on a circular track; a central reference clock(CRC) having an origin point at a center of the circular track; and aclock/sync connector coupled to the CRC through a zero skew clockconnection to one or more sync buses, wherein each instrument utilizesthe CRC to coordinate its testing process with another instrument.